The invention provides a delay circuit utilizing two timers and a minimum of logic to achieve a combination ON/OFF delayed function. The output signal is used to inhibit the ON delay timer, and the circuit is fully resettable in both the ON delay and OFF delay modes.
The invention overcomes disadvantages of pivot delay circuits having an ON delay and OFF delay timer in series. In the series arrangement, each reset time is dependent on the other timer. For example, if the input signal switches ON-OFF-ON before the end of the first ON delay, the second or reset ON delay may have to wait until the end of the OFF delay before beginning retiming.
In the present invention, the timers may be reset independently of each other such that each respective ON or OFF delay function may begin retiming without waiting for the other delay function if the input signal changes states before the end of the respective ON or OFF delay.
The invention is characterized by expanded timing range, reduced power consumption and improved resolution. Though not limited thereto, the delay circuit was developed for proximity switches and is particularly useful in photoelectric type proximity switches for providing a delayed output signal following a given sensed condition. The wide range together with the low power consumption makes the circuit ideal for such proximity switch applications.